1. Field of the Invention
The present invention generally relates to a multiple communication system for vehicular bodies. More particularly, it relates to a multiple communication system for vehicular bodies such as automobiles, of the type which includes a plurality of job units each respectively provided with one or more detection implements for obtaining data by detecting the status of detection objects such as a sensor and a switch, and with one or more electrical loads such as a lamp, an indicator, and a pump to be driven on the basis of data obtained at other job units
2. Description of Prior Art
Recently, in the automotive art typically representing the field of vehicular bodies, there have been developed and put into practice a variety of control units, accompanied by an increased degree of complexity, as well as the enlargement of scale, in a signal transmission system, with the intensified tendency to complicate and scale up its wiring harness. In this respect, for the purpose of system rationalization, and particularly for the simplification of the wiring harness, there has been proposed a number of multiple communication systems for vehicular bodies, in which various signals are composed to be multiplied to thereby permit their transmission through a wiring harness with a smaller number of conductors.
One successful example of such conventional multiple communication systems is proposed in Japanese Patent Lay-Open Print No. SHO57-32155 filed on Feb. 2, 1980, of which the entire system structure is illustratively shown in FIG. 19 of the accompanying drawings.
In FIG. 19, generally designated at reference numeral 500 is a multiple communication system including a plurality of terminal units 514l to 514-p having their digital signal sources S.sub.l to S.sub.k, digital electric loads l.sub.1 to l.sub.l, analog signal sources M.sub.l to M.sub.m, and analog electric loads L.sub.l to L.sub.n, respective pairs of address signal lines 512A-1, 512A-2 and data signal lines 513D-d, 513D-a each commonly connected to all of the terminal units 514-1 to 514-p, and an address signal source 511 connected to supply an address signal to the address signal lines 512A-1, 512A-2. The address signal has a data structure consisting of eight bits, in which those four bits occupying upper places are output through one address signal line 512A-1 and the remaining four bits, put in lower places, through the other address signal line 512A-2. Of the data signal lines 513D-d, 513D-a, one (513D-d) is adapted for digital data signals and the other (513D-a) for analog data signals. The address signal source 511 is designed so as to produce a series of address signals up to a maximum of 256 locations. Each address signal reaching the respective terminal units 514-1 to 514-p is deemed to be of the same phase.
The communication system 500 has such a function that, when an address signal is produced, a data signal is output from one terminal unit 514-m to the data signal line 513D-d or 513D-a in accordance with the real-time status of such a digital or analog signal source of the terminal unit 514-m that is identified by the produced address signal, and such a digital or analog electric load of another terminal unit 514-n that is identified by the address signal is driven on a real-time basis in accordance with the output data signal on the data signal line 513D -d or 513D-a. Namely, any address signal identifies a digital or analog signal source of one particular terminal unit and a digital or analog electric load of another particular terminal unit so that, when the address signal is produced, a data signal is to be output from the corresponding signal source of the former terminal unit and the corresponding electric load of the latter terminal unit is to be driven in accordance with the data signal.
In such a conventional multiple communication system for vehicular bodies, a plurality of terminal units have a signal transmission network thereamong consisting of a pair of address signal lines and a pair of data signal lines, thus effectively preventing the wiring harness from becomming complicated and large-sized, thereby permitting improved facilitation of system maintenance.
In such a multiple communication system, however, any data signal from any data signal source of any terminal unit is required to be processed at the same time when an address signal source has produced an address signal identifying the data signal source, thus practically permitting no long-time operations to be controlled by such data signals.
Moreover, in such a communication system, no consideration is provided for informing, when any data signal source or electric load of any terminal unit is caused to malfunction, a driver of the malfunction, so that the system would continue working even when trouble develops at such a terminal unit.
Incidentally, in such a system, some of those terminal units located at particular portions of a certain vehicular body may be provided with an electric load that needs an extremely quick response. For example, the system may have an electric horn or a brake lamp which are required to quickly respond without delay when a driver operates a horn switch or pedals a brake. In this respect, such a system, however, is unsuccessfully adapted to quickly transmit a data signal, from a terminal unit for detecting an operator's operations such as to a horn switch and a brake, to another terminal unit controlling corresponding electric loads such as an electric horn and a brake lamp.
Further, such a system is provided with an address signal producer which, when caused to malfunction, disables the signal transfer among terminal units, thus undesirably adversely affecting the function of the entire system.
The present invention has been achieved to effectively overcome such disadvantages in a conventional multiple communication system for vehicular bodies.